I can't tell from the photos what the problem is. I would cut out the dead branches and take them to your local Extension Office (They are located at 317 S. Third St. if Bardstown, Call them at 502.348.9204) Ask to speak to Robbie Smith. He's the Horticulture agent. He can help.
There may be a canker on the stem that is causing the problem or It may be something else. Please ask Robbie about proper pruning practices. I see some stubs that may be an entry for more disease and insect problems.